Buggy code:
public class HandlerAddHandler extends AbstractAddStepHandler { static final HandlerAddHandler INSTANCE = new HandlerAddHandler ( ) ; private HandlerAddHandler ( ) { } static void launchServices ( final OperationContext context , final PathAddress pathAddress , final ModelNode model , final ServiceVerificationHandler verificationHandler , final List < ServiceController < ? > > newControllers ) throws OperationFailedException { Handler newHandler = new Handler ( ) ; <START_BUG> ModelNode classNameNode = CLASS_NAME . resolveModelAttribute ( context , model ) ; <END_BUG> ModelNode codeNode = CODE . resolveModelAttribute ( context , model ) ; String typeName ; if ( classNameNode . isDefined ( ) ) { typeName = classNameNode . asString ( ) ; } else if ( codeNode . isDefined ( ) ) { typeName = HandlerTypeEnum . forType ( codeNode . asString ( ) ) ; } else { throw ROOT_LOGGER . federationHandlerTypeNotProvided ( ) ; } newHandler . setClazz ( typeName ) ; ModelNode handler = Tools . readModel ( context . readResourceFromRoot ( pathAddress ) ) ; if ( handler . hasDefined ( COMMON_HANDLER_PARAMETER . getName ( ) ) ) { for ( Property handlerParameter : handler . get ( COMMON_HANDLER_PARAMETER . getName ( ) ) . asPropertyList ( ) ) { String paramName = handlerParameter . getName ( ) ; String paramValue = VALUE . resolveModelAttribute ( context , handlerParameter . getValue ( ) ) . asString ( ) ; KeyValueType kv = new KeyValueType ( ) ; kv . setKey ( paramName ) ; kv . setValue ( paramValue ) ; newHandler . add ( kv ) ; } } SAMLHandlerService service = new SAMLHandlerService ( newHandler ) ; PathElement providerAlias = pathAddress . subAddress ( 0 , ( ( pathAddress . size ( ) ) - 1 ) ) . getLastElement ( ) ; ServiceTarget serviceTarget = context . getServiceTarget ( ) ; ServiceBuilder < SAMLHandlerService > serviceBuilder = serviceTarget . addService ( createServiceName ( providerAlias . getValue ( ) , newHandler . getClazz ( ) ) , service ) ; ServiceName serviceName ; if ( providerAlias . getKey ( ) . equals ( IDENTITY_PROVIDER . getName ( ) ) ) { serviceName = IdentityProviderService . createServiceName ( providerAlias . getValue ( ) ) ; } else { serviceName = ServiceProviderService . createServiceName ( providerAlias . getValue ( ) ) ; } serviceBuilder . addDependency ( serviceName , EntityProviderService . class , service . getEntityProviderService ( ) ) ; if ( verificationHandler != null ) { serviceBuilder . addListener ( verificationHandler ) ; } ServiceController < SAMLHandlerService > controller = serviceBuilder . setInitialMode ( PASSIVE ) . install ( ) ; if ( newControllers != null ) { newControllers . add ( controller ) ; } if ( ! ( context . isBooting ( ) ) ) { context . reloadRequired ( ) ; } } @ Override protected void populateModel ( ModelNode operation , ModelNode model ) throws OperationFailedException { } @ Override protected void performRuntime ( OperationContext context , ModelNode operation , ModelNode model , ServiceVerificationHandler verificationHandler , List < ServiceController < ? > > newControllers ) throws OperationFailedException { } }

Fix:
ModelNode classNameNode = CLASS . resolveModelAttribute ( context , model ) ;